|  | Initial exposure statusa | |
---|---|---|---|
 | Exposedb | Unexposedc | Total |
Selected | 1,492 | 1,704 | 3,196 |
Excluded during enrollment | Â | Â | Â |
  Never located | 132 (8.8) | 136 (8.0) | 268 (8.4) |
  No response | 245 (16.4) | 336 (19.7) | 581 (18.2) |
  Ineligible | 7 (0.5) | 8 (0.5) | 15 (0.5) |
  Refusal | 149 (10.0) | 137 (8.0) | 286 (8.9) |
Returned questionnaire | Â | Â | Â |
  Percent of located | 959 (70.5) | 1,087 (69.3) | 2,046 (69.9) |
  Percent of selected | 959 (64.3) | 1,087 (63.8) | 2,046 (64.0) |
Excluded during exposure assessment and analysis | Â | Â | Â |
  Incalculable exposure—insufficient data for geocoding residential address | 60 (6.3) | 75 (6.9) | 135 (6.6) |
  Incalculable exposure-missing data on LMP | 20 (2.1) | 21 (1.9) | 41 (2.0) |
  Multiple birth | 11 (1.2) | 21 (1.9) | 32 (1.6) |
  Birth anomaly | 22 (2.3) | 32 (2.9) | 54 (2.6) |
  Missing data on key covariates | 9 (0.9) | 9 (0.8)d | 18 (0.9) |
Final sample | 834 | 932 | 1,766 |